A phase IV, open-label trial using bortezomib for retreatment of patients (pts) with multiple myeloma (MM) following an initial response to bortezomib

17539 Background: Bortezomib (VELCADE; Vc) has substantial single agent activity in heavily pretreated patients. Response rates have been shown to improve when used in combination with other agents. Since some pts experience long durations of response with treatment-free periods, this open-label, single-arm study was designed to determine the utility of retreatment with Vc alone or in combination with dexamethasone, thalidomide or liposomal doxorubicin. Methods: Pts who previously responded to Vc alone or in combination are eligible for this study. Up to 78 pts will receive Vc alone or in combination at the finishing dose of their initial Vc treatment (0.7, 1.0, or 1.3 mg/m2) as a bolus, intravenous injection on days 1, 4, 8, and 11 of a 21-day treatment cycle. Responses are assessed by the investigators and also calculated from percentage reduction in serum or urine M-protein. Results: To date, 15 pts have been treated and 12 are evaluable for response (having received at least 2 cycles of therapy). 8/12 patients had dexamethasone added to their regimen. The population is representative of pts with relapsed and refractory MM: mean age, 68 years; 4 males, 8 females; median of 5 prior lines of therapy; and 67% IgG MM. Median treatment-free period between the end of first Vc treatment and the start of retreatment: 11.1 months (range 5–21 months). Investigator-assessed responses show that 50% of pts have achieved a PR or CR. Only 1 pt had progressive disease. One pt has developed new peripheral neuropathy, while pre-existing neuropathy has worsened in 4 pts. No Vc-related serious adverse events have been reported. Conclusions: Preliminary results show that retreatment with Vc alone or in combination has encouraging activity with manageable toxicity even in pts who are heavily pretreated. These data suggest that repeated use after a treatment break may achieve prolonged disease control. This is the first report of Vc retreatment for MM. [Table: see text]